This invention relates to the monitoring of the operation of an electrolytic cell particularly a plurality of cell units of one or a plurality of cells having an electrode comprising a plurality of moving electroconductive particles which either serve and act as the electrode itself or are continuously or intermittently and successively in electronic contact with a parent electrode and thereby produce an electrochemical reaction. This reaction may involve generation of electricity as in a battery or may involve a chemical reaction producing or releasing an element or compound, for example chlorine, electrodeposited metal, etc.
It is known to conduct electrochemical reactions in a cell having an electrode comprising a plurality of electroconductive particles. Thus, U.S. Pat. No. 3,879,225 granted to J. R. Backhurst et al., describes and illustrates a cell wherein a fluidized bed of conductive particles is established in a contact with a parent electrode or conductor to conduct an electrochemical reaction. The particles are supported by an upward flow of electrolyte and move about continuously to establish a bed of moving particles which may be continuously or periodically in electrical contact with each other and/or with the parent electrode and the bed of moving particles effectively becomes, or may be regarded as, the electrode since the electrodic reaction eventually or even continuously takes place on the surface of the tumbling particle at least while it is in contact with the parent electrode or conductor. Various other patents describe other electrodes comprising moving particles including but not limited to the following:
______________________________________ U.S. Pat. No. BRITISH ______________________________________ 3,981,787 3,887,400 1,098,837 3,902,918 1,789,443 3,703,446 3,654,098 3,781,787 ______________________________________
The body of particles need not be in the form of a fluidized bed which usually comprises a body of tumbling, bouncing, or dancing particles with a well-defined upper surface and more or less uniform density. It may also comprise a moving stream or layer of particles flowing along an inclined parent electrode or a wall or may even comprise a circulating stream of particle slurry which flows in a path along parent electrode or conductor. One advantage of this type of electrode, the moving particulate electrode, is that an increased area of electrochemically active electrode surface is provided due to the high exposed surface area of the electrode particles.
In the operation of this type of cell, it is desirable that the density of the bed (number of particles per unit volume of active area) be maintained relatively uniform or that the rate of movement be maintained continuously and settling minimized and thus that particle movement be maintained at least within a certain degree of control.
Several problems may arise:
For example, irregular flow of fluid medium producing the particle movement may develop through blockage of parts thus causing channeling and producing a bed of varying particle population or density from one side to the other of an electrode bed. A change in particle density or size, for example, in electrodeposition, may induce the particles to settle thus lowering the effective height of the bed. These are only some of the factors which cause variation.
This variation may thus occur across the width of the electrode as where one side or a central area is less dense than another, due for example to variation in velocity of the upward lifting fluid stream. It may also occur from top to bottom of the bed particularly where the particles change in diameter or individual weight or density during the reaction and thus tend to seek a different level in the upwardly moving stream.
The problem of monitoring such variation becomes increasingly complicated when a plurality of cells are used. For example, a plurality of cell units may be aligned in electrical series and the number of units may even be in the hundreds. Since the cell tanks or enclosures are usually opaque monitoring of the many cells may be difficult.